1. College of Veterinary Medicine, Shaanxi Stem Cell Engineering and Technology Research Center, Northwest A&F University, Yangling 712100, Shaanxi, China
2. College of Agriculture, Guangdong Ocean University, Zhanjiang 524088, China
3. Key Laboratory for Mammalian Reproductive Biology and Biotechnology, Ministry of Education, Inner Mongolia University, Hohhot 010021, China